Wireless power transmitter implementing multiplexing for monitoring circuitry in a semiconductor device

Abstract

In an embodiment, a semiconductor device is disclosed that comprises a multiplexer. The multiplexer is configured to receive signals from each of a plurality of transmission coils of a wireless power transmitter as inputs and to output an output signal based at least in part on one of the signals. The semiconductor device further comprises an attenuator connected to the multiplexer that is configured to adjust a voltage of the output signal. The attenuator comprises a variable resistance. The semiconductor device further comprises a plurality of pull down circuits each corresponding to one of the transmission coils. The pull down circuits are configured to selectively clamp the signals received from the corresponding transmission coils to ground.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a multiplexer, the multiplexer being configured to receive signals from each of a plurality of transmission coils of a wireless power transmitter as inputs and to output an output signal based at least in part on one of the signals; 
 an attenuator connected to the multiplexer and being configured to adjust a voltage of the output signal, the attenuator comprising a variable resistance; and 
 a plurality of pull down circuits each corresponding to one of the transmission coils, the pull down circuits being configured to selectively clamp the signal received from the corresponding transmission coil to ground. 
 
     
     
       2. The semiconductor device of  claim 1 , wherein the plurality of pull down circuits are selectively activatable by a controller to selectively clamp the signals received from the corresponding transmission coil to ground. 
     
     
       3. The semiconductor device of  claim 2 , wherein the plurality of pull down circuits comprise field effect transistors that are selectively activatable by the controller to selectively clamp the signals received from the corresponding transmission coil to ground. 
     
     
       4. The semiconductor device of  claim 1 , wherein the variable resistance of the attenuator is adjustable by a controller to adjust the voltage of the output signal. 
     
     
       5. The semiconductor device of  claim 4 , wherein the semiconductor device further comprises a monitoring circuit, the monitoring circuit being configured to measure characteristics of the output signal when the voltage is within a target measurement range. 
     
     
       6. The semiconductor device of  claim 5 , wherein the monitoring circuit comprises foreign object detection circuitry, the foreign object detection circuitry being configured to determine whether or not a foreign object is located within a magnetic field generated by the transmission coil based at least in part on the received signals from each of a plurality of transmission coils. 
     
     
       7. The semiconductor device of  claim 5 , wherein the variable resistance of the attenuator is configured to be progressively adjusted by the controller until the voltage is within the target measurement range. 
     
     
       8. The semiconductor device of  claim 5 , wherein the variable resistance of the attenuator is configured to be set to a target resistance value by the controller before the controller selectively unclamps the received one of the signals from ground using the corresponding pull down circuit, the target resistance value being configured to cause the voltage of the output signal to be smaller than a maximum voltage sustainable by the semiconductor device. 
     
     
       9. The semiconductor device of  claim 8 , wherein the controller is configured to set the variable resistance of the attenuator to the target resistance value before causing the multiplexer to transition from outputting the output signal based at least in part on the signal received from a first of the plurality of transmission coils to outputting the output signal based at least in part on the signal received from a second of the plurality of transmission coils. 
     
     
       10. A wireless power transmitter comprising a controller, the controller being configured to:
 cause a first pull down circuit of the wireless power transmitter to clamp a first transmission coil of a plurality of transmission coils to ground, the plurality of transmission coils being connected to the wireless power transmitter; 
 cause a resistance of an attenuator of the wireless power transmitter to be set to a target resistance value; 
 control a multiplexer of the wireless power transmitter to transition from a selection of the first transmission coil to a selection of a second transmission coil of the plurality of transmission coils for output by the multiplexer, the multiplexer being configured to output a signal based at least in part on the selection of the second transmission coil; 
 cause a second pull down circuit of the wireless power transmitter to unclamp the second transmission coil from ground; 
 cause the resistance of the attenuator to be progressively adjusted until a voltage of the signal is within a target voltage range; and 
 receive monitoring data from a monitoring circuit of the wireless power transmitter, the monitoring circuit being configured to generate the monitoring data based at least in part on the signal. 
 
     
     
       11. The wireless power transmitter of  claim 10 , wherein when the controller is configured to determine that each other transmission coil of the plurality of transmission coils is already clamped to ground by a corresponding pull down circuit of the wireless power transmitter before causing the second pull down circuit to unclamp the second transmission coil from ground. 
     
     
       12. A wireless power transmitter comprising:
 a plurality of transmission coils; and 
 a semiconductor device comprising:
 a multiplexer, the transmission coils being connected to the multiplexer as inputs, the multiplexer being configured to select one of the transmission coils and output a signal based at least in part on the selected one of the transmission coils; 
 an attenuator connected to the output of the multiplexer, the attenuator comprising a variable resistance; and 
 a monitoring circuit connected to the output of the multiplexer and configured to measure at least one characteristic of the selected one of the transmission coils based at least in part on the signal output by the multiplexer. 
 
 
     
     
       13. The wireless power transmitter of  claim 12 , wherein the semiconductor device further comprises a pull down circuit connected to at least one of the transmission coils and being configured to selectively clamp the at least one of the transmission coils to ground. 
     
     
       14. The wireless power transmitter of  claim 13 , wherein the pull down circuit comprises a field effect transistor, the field effect transistor being activatable to selectively clamp the at least one of the transmission coils to ground. 
     
     
       15. The wireless power transmitter of  claim 13 , wherein the pull down circuit comprises a plurality of pull down circuits, each pull down circuit being connected to a corresponding transmission coil and being configured to selectively clamp the corresponding transmission coil to ground. 
     
     
       16. The wireless power transmitter of  claim 12 , further comprising a plurality of resistors, each resistor being connected in serial between a corresponding one of the transmission coils and the semiconductor device. 
     
     
       17. The wireless power transmitter of  claim 12 , further comprising a controller, the controller being configured to:
 adjust the resistance of the attenuator; and 
 control the multiplexer to select the one of the transmission coils. 
 
     
     
       18. The wireless power transmitter of  claim 17 , wherein the monitoring circuit comprises foreign object detection circuitry, the foreign object detection circuitry being configured to measure the signal output by the multiplexer. 
     
     
       19. The wireless power transmitter of  claim 18 , wherein the foreign object detection circuitry is configured to measure voltages in a voltage range that is smaller than a voltage of the selected one of the transmission coils, the attenuator being configured to adjust the voltage of the signal output by the multiplexer. 
     
     
       20. The wireless power transmitter of  claim 19 , wherein the controller is configured to progressively adjust the resistance of the attenuator until the voltage of the signal is within the voltage range.